v20210802 * performance optimizations for automatic indentation * lua-skip-ws-and-comments-forward, lua-skip-ws-and-comments-backward: add new functions * lua-comment-start-pos: make sure point inside comment starter "--" is considered inside comment * lua-funcname-at-point: refactor to avoid copying syntax table to improve performance * lua--signum: add backward compat helper * code cleanups & minor refactors